Climate Change Assessments for the Gaula River
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Kamrun Naher Kamrun 2019 thesis Master's NTNU Norwegian University of Science and Technology Master's thesis Faculty of Engineering Department of Civil and Environmental Engineering July 2019 the GaulaRiver Climate ChangeAssessmentsfor Kamrun Naher Climate Change Assessments for the Gaula River Kamrun Naher Hydropower Development Submission date: July 2019 Supervisor: Knut Alfredsen Co-supervisor: Abebe Adera Norwegian University of Science and Technology Department of Civil and Environmental Engineering NTNU Faculty of Engineering Norwegian University of Science and Technology Science and Technology Department of Hydraulic and Environmental Engineering M.Sc. THESIS IN HYDROPOWER DEVELOPMENT Candidate: Kamrun Naher Title: Climate change assessments for the Gaula river. 1 BACKGROUND The rise in global temperature provide challenges for the management of water resources, related to water availably, timing of runoff and changes in extremes as reported in numerous studies. Much focus has been on the extreme values and particularly extreme precipitation and floods. But changes in climate will have an effect on several components of the hydrological cycle, and also on river hydraulics, water temperature, sediment processes, vegetation and other elements of the catchment. Further, these factors will influence the use of water in rivers and lakes both for industrial, municipal and recreational use. In this thesis we will study climate change and impacts on changed flow on processes in the Gaula catchment in Norway. Based on downscaled precipitation and temperature from the Norwegian Climate Service Center we will evaluate the impacts on flow regime changes, river flow and associated processes. In addition, effects on hydropower production in Lundesokna will be evaluated. 2 MAIN QUESTIONS FOR THE THESIS The thesis shall cover, though not necessarily be limited to the main tasks listed below. The following main steps will be carried out during the thesis work: 1. Literature review on climate impacts on flow regimes changes in northern regions, associated water quality issues (like temperature) and hydropower production. The review should build a i foundation for the further work. 2. Prepare climate data for the region and provide an overview of changes in the driving factors like precipitation and temperature. This should include both magnitude and timing of high and lows and the variability of each variable. 3. Run the PINEHBV model for Gaula to prepare runoff series for the climate data prepared in 2). This should build on work done for the Gaulfoss gauge by Lars de Graaff in his ongoing thesis. It should be discussed if other gauges could be useful for the analysis. 4. Do an analysis of the effect climate has on the power production in the Lundesokna power system. Model setup and data for this analysis will be provided, and more information can be found in Casas-Mulet et al. Fisheries Management and Ecology, 2014. 5. Setup of the HEC-RAS model for Gaula (reach to be decided later) to model flow and water temperature. Investigate the effect of a warming climate on the water temperature in the river. Evaluate the applicability of the model to estimate water temperature in the future climate. 6. Evaluate how changes in temperature and other factors would influence catchment vegetation and evapotranspiration. Investigate if this can be modelled and how this could be implemented. 3 SUPERVISION, DATA AND INFORMATION INPUT Professor Knut Alfredsen will be the formal supervisor the thesis work. Abebe Girmay Adera will assist with processing climate data for the project. PhD-student Jo Halvard Halleraker is working on catchment management in Gaula and will be available for discussions and input for the analysis. Discussion with and input from colleagues and other research or engineering staff at NTNU, SINTEF, power companies or consultants are recommended. Significant inputs from others shall, however, be referenced in a convenient manner. The research and engineering work carried out by the candidate in connection with this thesis shall remain within an educational context. The candidate and the supervisors are therefore free to introduce assumptions and limitations, which may be considered unrealistic or inappropriate in a contract research or a professional engineering context. 4 REPORT FORMAT AND REFERENCE STATEMENT The thesis report shall be in the format A4. It shall be typed by a word processor and figures, tables, photos etc. shall be of good report quality. The report shall include a summary, a table of content, a list of literature formatted according to a common standard and other relevant references. A signed statement where the candidate states that the presented work is his own and that significant outside input is identified should be included. ii The report shall have a professional structure, assuming professional senior engineers (not in teaching or research) and decision makers as the main target group. The thesis shall be submitted no later than 11th of June 2018. Trondheim 15th of January 2018 ___________________________ Knut Alfredsen Professor iii ABSTRACT The effects of climate change were assessed for Gaula, south of Trondheim in Norway as a wetting winter and drying summer are predicted to occur in the future. The research was done in six steps to find the effect of a warming climate in Gaula. Ten climate models with two emission scenarios were used since there is uncertainty in both natural and anthropogenic changes. Periods 2040-2069 and 2070-2099 were compared with period 1976-2005 and the climate data was downloaded from https://nedlasting.nve.no/klimadata/kss. In the beginning, the climate model’s data was checked with the observed data and then the climate data was used to obtain future changes in precipitation, temperature and runoff. For all scenarios, it was found that the precipitation, temperature and runoff are increasing. Summer precipitation increase is extreme, and the runoff is changing seasonally. An increasing precipitation will lead to frequent floods and temperature rise to droughts. The spring peak is reduced and moved. Compared to the control period the increase in annual runoff is not so high 0.9, 4.7, 2.7 and 5.6% for RCP4540, RCP4570, RCP8540 and RCP8570 respectively. Snowpack reduction (70%) is highest for RCP8570 due to high air temperature. Future runoff was scaled and taken to the nMAG model to find the effect of climate change on Lundesokna power plant in the current strategy. The result achieved showed that there is a small increase in annual power production for future climate scenarios. However, the annual change in inflow is zero and the production is increasing in winter and decreasing in summer following the higher winter flow and lower summer flow. Sama power plant will be benefited most among the other power plants (maximum 8.84% annual increase for RCP8570). To observe the effect of drying summer and wetting winter, January 5 percentile and July 25 percentile flow were simulated in HEC-RAS5.0.6. The reach was selected from Haga bru station to Trondheim fjord and a steady flow analysis was done to observe the drying and wetting conditions in Gaula. Results obtained showed that drying summer and wetting winter have effects on the river and these drying areas will lead to vegetation, fish migration problems, water quality deterioration in the future. High flow in winter might improve the salmon fish conditions, still there is uncertainty regarding other species and chemical processes in the river. Water temperature in Gaula was measured only for RCP8570. The average temperature is increasing in water by 1.97oC for RCP8570 compared to the control period. Minimum summer temperature obtained from this research is 6.8oC in future whereas for the control iv period it is 0.6oC. Increasing water temperature has many impacts regarding species in the river and agricultural problems. Summarizing the results, it can be said that, Gaula is having a different hydrograph in future climate and snowpack is reducing tremendously. Since tourism and recreational activities in Norway depend on snow, this might affect severely. The increasing runoff will give higher production for hydropower in present strategies. In contrast to that, future consumption and electricity price would be different, thus the power company needs to take adaptive strategies in the future. Though in winter, increasing runoff might improve the salmon fishing in Gaula, there remains uncertainty in the water quality for both summer and winter since both low and high flows have their changing capability to the aquatic ecosystem in different ways. Nevertheless, further research is recommended on the power production using adaptive strategies and also for the ecosystem change in Gaula since the ecosystem has a great influence on the aquatic species, agriculture, recreation, human health, etc. Figure A: Altered hydrological regime for Gaula in a warming climate v ACKNOWLEDGEMENT Foremost, I would like to express my gratitude to my supervisor Prof. Knut Alfredsen for the remarkable support in my thesis, for his patience, motivation, enthusiasm, and immense knowledge. His guidance helped me in the time of research and writing of this thesis. I could not have imagined having a better supervisor and mentor for my study. This thesis dealt with a massive amount of data which was not easy to process, and I got continuous direction from my professor about processing, using the right software/tools and getting precise outcomes. Special thanks to the Department of Hydraulic and Environmental Engineering, NTNU for giving me the opportunity to use the lab with multiple computers which was urgent to finish the thesis within a limited time. Multiple computers accelerated the speed of my task greatly that was impossible with a single computer. Besides, I would like to thank Abebe Adera at NTNU who contributed in this thesis time to time with proper help and advises. Last but not the least, I express my gratitude to my family for providing continuous support and encouragement throughout my years of study and my friend Elhadi, who helped and encouraged me a lot during this thesis.